The invention concerns a switch blade rolling device of the type having a rolling support.
Various devices for supporting a railroad switch blade are known, including those with a rolling support. The main purpose in most new devices in this area is to reduce the handling force needed for switching, and reducing or eliminating the need for periodically lubricating said device.
According to German patent DE 361444, the switch blade is carried on a free rolling cylinder. Before the blade comes to a stock rail, the cylinder moves down from a higher part of a supporting plate. The switch blade seats with its full load on slide chairs. Then the movement of the switch blade finishes with a full translation force needed. When the switch blade begins to move back, an even greater force is needed.
In U.S. Pat. No. 1,599,733, the switch blade moves above a horizontally oriented member, rolling on a resiliently mounted roller. The clearance between the blade and sliding chairs is adjustable. The clearance does not change during all the movement, so that the switch blade is seated down on the slide chairs at the same time the load from an approaching wheel of a railroad vehicle is applied. The sudden seating of the switch blade causes undesirable impacts, such as kick bounces.
In German patent DE 1056641, the switch blade moves on a plurality of rollers, mounted in one block which is resiliently carried in a housing. The housing is connected to the stock rail foot by a bracket and clamping claw. The movement of the switch blade occurs under a constant upward force from rollers, which " . . . is adjustable to a predetermined height and to a horizontal position." The block with rollers is closely mounted in its housing and sealed. In this way a cavity is created, which, disadvantageously can fill with water through an aeration opening and, upon freezing, eliminates the resilient function of the device.
Also a group of East German patents (Nos. DD 56536, DD 61558, DD 64069, DD 66638 and DD 67140) shows devices having switch blades resiliently carried and transported above a longitudinal member. Said member is created in the form of a lever of the second kind, where during the transport of the switch blade over said member towards the stock rail, the upward force decreases. This decrease can cause the switch blade to seat on slide chairs before it finishes the movement to the stock rail. In a physical embodiment of the design, the upward force changes only slightly, which is insufficient for reliable adjustment of the seating moment of the blade using only the stock rail. The specifications of these patents describe all the movement of the blade as provided in a position slightly lifted above the slide chairs. Thus, kick bounces after the sudden seating of the switch blade on the slide chairs are not eliminated.
The above mentioned East German patents disclose that the longitudinal member is connected (by bolts or by welding), by means of a transverse member, to the slide chairs which are mounted on sleeper. This support system creates new forces among the sleeper, the slide chairs and the rail, which forces were not previously considered, and so the devices are easily damaged or require more frequent repairs. The devices according to the above-mentioned DD patents require complicated installation, due to welding or due to dismounting of existing parts from the rail-sleeper unit.
According to published German application DE-OS 3420505, a switch blade is known, which moves over a special slide chair, rolling on at least two spheres, which are carried in a ball-system housing. After moving downward from the last sphere, the switch blade seats on the slide chairs with its full load. Then, a very large transport force is needed for finishing the movement of the switch blade to the stock rail.
Also the device according to published European patent application EP 0389851 is known, where an upward force on the switch blade is applied continuously during its movement between the two end-positions. The switch blade seats on slide chairs slightly before coming to the stock rail. However, the device is very large and heavy.